Visual Refresh: Firefox 2's theme and user interface have been updated to improve usability without altering the familiarity of the browsing experience. *

Built-in phishing protection: Phishing Protection warns users when they encounter suspected Web forgeries, and offers to return the user to their home page. Phishing Protection is turned on by default, and works by checking sites against either a local or online list of known phishing sites. This list is automatically downloaded and regularly updated when the Phishing Protection feature is enabled. *

Enhanced search capabilities: Search term suggestions will now appear as users type in the integrated search box when using the Google, Yahoo! or Answers.com search engines. A new search engine manager makes it easier to add, remove and re-order search engines, and users will be alerted when Firefox encounters a website that offers new search engines that the user may wish to install. *

Improved tabbed browsing: By default, Firefox will open links in new tabs instead of new windows, and each tab will now have a close tab button. Power users who open more tabs than can fit in a single window will see arrows on the left and right side of the tab strip that let them scroll back and forth between their tabs. The History menu will keep a list of recently closed tabs, and a shortcut lets users quickly re-open an accidentally closed tab. *

Resuming your browsing session: The Session Restore feature restores windows, tabs, text typed in forms, and in-progress downloads from the last user session. It will be activated automatically when installing an application update or extension, and users will be asked if they want to resume their previous session after a system crash. *

Previewing and subscribing to Web feeds: Users can decide how to handle Web feeds (like this one), either subscribing to them via a Web service or in a standalone RSS reader, or adding them as Live Bookmarks. My Yahoo!, Bloglines and Google Reader come pre-loaded as Web service options, but users can add any Web service that handles RSS feeds. *

Inline spell checking: A new built-in spell checker enables users to quickly check the spelling of text entered into Web forms (like this one) without having to use a separate application. *

Live Titles: When a website offers a microsummary (a regularly updated summary of the most important information on a Web page), users can create a bookmark with a "Live Title". Compact enough to fit in the space available to a bookmark label, they provide more useful information about pages than static page titles, and are regularly updated with the latest information. There are several websites that can be bookmarked with Live Titles, and even more add-ons to generate Live Titles for other popular websites. *

Improved Add-ons manager: The new Add-ons manager improves the user interface for managing extensions and themes, combining them both in a single tool. *

JavaScript 1.7: JavaScript 1.7 is a language update introducing several new features such as generators, iterators, array comprehensions, let expressions, and destructuring assignments. It also includes all the features of JavaScript 1.6. *

Updates to the extension system: The extension system has been updated to provide enhanced security and to allow for easier localization of extensions. *

Client-side session and persistent storage: New support for storing structured data on the client side, to enable better handling of online transactions and improved performance when dealing with large amounts of data, such as documents and mailboxes. This is based on the WHATWG specification for client-side session and persistent storage. *

SVG text: Support for the svg:textpath specification enables SVG text to follow a curve or shape. *

New Windows installer: Based on Nullsoft Scriptable Install System, the new Windows installer resolves many long-standing issues.

One of the few things I don't like about Firefox is the hassle of updating it - it always seems to break stuff (sometimes the whole browser), unlike an IE upgrade which is seamless. I think I'll probably leave FF2 until I do a completely new setup with Vista, once it's here - I think I'm still using 1.5.0.1 or something at the moment, as even the minor updates break it sometimes (I seem to remember problems with 1.5, and then 1.5.0.1 over that).

I've had the "can't launch Firefox because another installation is in progress" error, which is resolved by deleting various things from the Firefox directory, and I also had the thing where you try to load Firefox after updating and all the buttons/address box are gone except for the File, Edit... menus, and it's completely broken. I think that happened when I installed 1.5.0.1 over 1.5, and I had to reinstall 1.5 over that mess (and probably restore a profile backup) and then 1.5.0.1 again to get it back to normal. The latter problem also happened with 1.0.x when I had some extension problem, and I didn't have a profile backup then so had to start from scratch - that was probably the closest I've come to going back to IE, as it took hours to reinstall everything and get it back to how it was before.

It also took a long time to go from 1.0 to 1.5, as loads of my extensions wouldn’t update to the 1.5-compatible versions through the built-in updater, so I had to install them all manually. Also I have a lot of custom interface components (rounded address and search bar like on a Mac, Office 2003 style menus etc.) and they seem to subtly change the size of bits of the interface between major versions (or at least they did for 1.0 > 1.5), so I had to go through resizing all the graphics files to make it look right again.